Electrical x h heating unit



Nov. 13, 1923.

S. l. PHELPS ELECTRICAL HEATING UNIT Filed Fe b. 1a. 1922 Patented Nov. 13, 1923.

UNIT ED?- STA THIS SEBR'ING I. PHELPS, OF ROCKFORD, ILLINOIS.

ELECTRICAL HEATING UNITL Application filed February 15, 1922.- Serial No: 587,4'1'9.

To all whom it may concern:

Be it known that I. Smuuxc I. Pucnrs, a citizen of the United States of America. and a residentof Rockford, county of \Viunebago, andState of Illinois, have invented a new and useful Improvement. in Electrical l-Ieating Units; of which the following is a specification.

The main=objects of this invention are to PJ'DVidG aH'lHlPX'OTMl armored electric heating unit foruse in making up electrical heating! devices; to provide an improved construction ofthercore upon which the elec trical:resistanceis wound; to provide an improved-construction and arrangement-otterminral contucts -orr-the heating unit; to-pro vide'an-improved construction and manner of folding a metal sheath for the-resistancewound= core; to: provide an improved or rangementof. the-heatingunit with angula-rly disposed heatingsections; and-to proride-2v heating unit of this-kind which is :comparatively simple and inexpensive to manufacture and durable-and etiieient in opemtiomand which is particularly useful for use iniforming electricalTbroilershot plates androthe'n electrical appliances.

An'illustrative embodiment of this inventioniis shown in the accompanying: drawing; imwhich Figure-L is a" perspective-view, with the front thereof broken? away. ofan-electr-ical -='heating device commonly known as a hot. plti temade'up i with phmilityi of: separate heating am his constructed in accordance \ri th this v invention.

nigure 2r isirnenlarged perspective view iofone?ofthew-ompletcd-heating units made up-in accordsure iritluthis-intention. Figures?! is-:m-enlfrqgcd deta-il perspective showing: the umnneu in \vhiolithe coreis formed and" t-hir terminal (nut-act secure-rt of. one end of the howling. umtz shown in- Figrrrofi:

"Figurec eis an enlzugecl: aosssectional detail! on theheating'unit; the section: being takcuiuthe-vertical plane of one of theiterr minal contacts.

A heating, unit constructed-in accordancewith this invention embodies a core made up of a rather thick layer of'flexible insulating. nnucrial interposed between thinlayersof still' insulating material, and having the electrical resistance-spirally wouudon' themmand connected at its ends to termi- 00 mil contact, strips attached to the core-by being inserted through slots-formed'therein, suid resistance-wound, core beingsheathcd in a metal envelope from which it iSzPI'Ol) crl i' insulated and \vhichis-folded and com' G5 pressed about the cureso asto mu kethe-com nectiou of the contacts. firm without thense (if-any fasteninggmeans.

In the specific embodiment h'erein.-shownthe heating unit 1 comprises-a.- core2.ofisp.e Tu rial-construction upon: which the resistance material 3 is spirally wound, terminal contacts 4 secured to the'core -\vithoutithe use of auxiliary fastening, means, and :11 metal sheath or housing 5 "which-is foldcdaabouti the resistance-wound core 2. These-parts are so constructed and-arranged that-ar.plurality of these individual units- 1' may; boas-- scniblcd on a: frame-6 \iritlrthe p per: faces thereof disposed in thesame. horizontal plane to form a support, forniutensil and. with the contact members 4:" engaging bus bars 7- supportedon .the frame and'conneoted by suitable means to a source of electricity.

The core 2 is preferably made u :ofu-comparntirely thickiliiyer 8 of flexib e-but nonrigid material'such as asbestos interposed between thin layers 9 ofstifl' fixibleinsu lating; materialisuch as mica. Theepurposeiuminsti-in-tiiig therorc in thismannoi" |s=to i-on1l iuc.=bull\' comparative-rigidityorstifi'r ncssraud' flexibilityinform with economy in ronstmctiou.

.-\sbestosalone would provide tho. bulk and he emnmnieah iuconstructiom but u.- 05 \VUHlll' not afford! thenecessary rigidityor 1 ithnme Mira: tll('.'ll@' Ulll provider the! rt quired rigidiuu and: the.- necessarjflexibiliby: if used in comparatively-thin sheets;- arid-in:

I hau form-would, he. COOIIUHIliFtL-Lbllb itnv ouldnot providesutlicient blllki 0n: the: other hand if sheets-of miixnthi'cliienoughito pro= vide the necessary hulk were used. the core would not have sullicient flexibility. and its construction would not be economical.

A fairly thick or bulky core is advantageous in that in winding the resistance material 3 thereon sharp or abrupt bends are not formed in the resistance material at the edges of the core as would be the case with a thin piece of material and which, experi ence has shown, either so weakens the re sistance material at the bend or brings poi= tions of the material so close together that fusing of the resistance casily takes place. By providing a rather'bulky core as shown in Figure 3, the sharp bend ofthe resistance material 3 is avoided.

The core should be comparatively rigid or stiff so that it will hold its form throughout all the handling to which it must necessarily be subjected during the process of winding and folding the housing thereabout. 4 Mica alone would provide this necessary rigidity or stillness but if used in sheets thick enough to provide the desired bulk for the reasons just'mentioned it is so expensive as to prohibit its use. On the other hand if thin mice were used sharp bends would be formed in the resistance material 3 at the edges of the core with the consequent objections heretofore mentioned. A thick sheet of mica alsois objectionable in that it does not pro vide a core of suflicient. flexibility to permit the shaping of the unit as hereinafter more fully described.

A certain amount of flexibility in the core is essential in order to permit the metal sheath or'casing 5, after being: folded around the core," to be bent longitudinally of its length soar to provide the heating unit with angularly' disposed heating sections. Asbestos in itself would provide sufficient lexibilitybut is objectionable for reasons 'already mentioned and mica would provide sufiicientflexibility it made thin enough but it. also is objectionable for reasons already explained.

Therefore in order to provide a core having the desired bulk. flexibility and rigidity or stillness. it has been found necessary to combine a: thick layer of asbestos arranged between two: thin la yous of mica. uch a core eliminates sharp bends in the resistance. permits all the necessary handling withou causing injury thereto and is flexible enough to allow it to be bent Without breaking.

In order to a oid either the use of an auxiliary fastening means for securing terminal contact members to the core or the bringing of the resistance material out through the housing and attaching it to contact members secured to the heating unitextraneous of the core, the terminal contacts 4 as herein shown comprise strips of metal bent intermediate their ends to provide offset portions 10 and 13173.net;

ll s arranged that when the strips are ex tended through slots 12 inthe corc these olfsct portions 10 and It bear against opposite faces of the core 2 on opposite sides of the respective slots. Electrical connection with the resistance material 3"is'madc by extending the ends 13 through the slots 12 so as to locate them between one of the offset portions of the respective contacts and the adjacent face of thc core as illustrated in Figure 3. The lower ends of the contact mem hers a re doubled upon themselves to provide clips l4 which are adapted to yieldingly grip in a rather firm way the bus bars 7. The contacts 4 are preferably twisted as shown at 15 so as to dispose the clips 14 at right angles to the plane of the core 2.

The envelope or sheath 5' is cut' out from sheet metal to provide'a body part 10; transversely disposed flanges 17 and 18-estending along the lateral edges thereof and'angularly disposed fingers 1.9 and 20 formcdat the ends of the bod part. 'The flange 17-is somewhat narrower than theflange 18whicb is of sufficient-length so that it will fold over 90 flange l7. At its ends the flange l8is'termii the core 3 withthe edge thereof close to the natcd short ofthefingers 20'so as'to provide an openingwhen the partsare all folded over. out through which the terminal con tacts 4 extend:

The core 2 withgresistance material3 wound thereon and with the terminal con-' tacts 4 attached is placed'in the metal envelopc. from which it is properly insulated by thin sheets of mica'or other insulating material. and'the flanges l'l and 18 and the fingers l9-and 20 folded tliereabout 'ina manner similarto=thatshownin Figures 2,: In folding the'se part'sthey are 5 and 6. firmly pressed toget-her sm as to" make the unit as thin as possible and also clamp parts down against the terminal contacts 4=so that without the use of any otherfastening means the contacts areifirmly held=in place-(in the units. I

use in making up heating devices-of various kinds such as broilers hot plates, and the like. They are usually assembled side by side in arallel relation on--'a frame similar to that indicated by Figure 1. The unit is simple and inexpensive to construct-and, because of the absence of-sharp bends in'the V .uo For many uses the'heating unit 1 is pref erahly provided with" angularly disposed l'ieating unit with angularly resistance material and the elimination of connections of the resistance material to terminal contacts extraneous of the core or by means of auxiliary fastening means, is extremely durable since all chances of fusing have been eliminated.

Although but one specific embodiment of this invention has been herein shown and de scribed, it will be understood that numerous details of the construction shown may be altered or omitted without departing from the spirit of this invention as defined by the following claims.

I claim-:

1. An-electrical heating unit comprising a core formed of a sheet of bulky flexible 1nsulating material interposed between sheets of thin stiff insulating; material, electrical resistance wound spirally on the outside of said core and asheath surrounding said resistancewound core and insulated therefrom.

2. Anelectrical heating unit com prising' a core formed of a sheet of asbestos interposed between sheets of mica, electrical resistance wound spirally on said core, and a sheath surroundino said resistance-Wound core and insulated therefrom.

3. An electrical'heating unit comprisin a core formed of a long narrow rectangular strip of asbestos interposed between strips of mice, said strip of asbestos being coin aratively thick and said strips of mica eing thin, electrical resistance comparative] wound spirally on said core, and a metal sheath enclosing said resistance-wound core and insulated therefrom.

An electrical heating unit com arising a core formed of a sheet of bulky flexible in- Sulating material interposed between sheets of thin stifi insulating material, electrical resistance wound spirally on said core amet-al sheath surrounding said resistance-wound core and insulated therefrom, and bent longitudinallv so as to form said heating unit with ngularly disposed heating sections.

5. An electrical heating unit comprising a core formed of a long narrow rectangular strip of asbestos interposed between strips of mice, said strip of asbestos being comparatively thick and said strips of mica being r:omp:alrati'veh thin. electrical resistance wound spirally on said core, and a metal sheath enclosing. said rcsistance-wouru] core and insulated therefrom and bent longitudine-11y near one edge so as to form said disposed heatin sections of relatively different widths.

6-. An electrical heating unit comprising, a core hai-ing a slot formed the chi at a predetermined point, resistance material wound. spirally on said core, an electrical contact in the form of a strip of metal inserted through said slot and having portions thereof abutting against opposite faces of said core with a portion of said resistance clamped between the strip and core and a metal sheath enclosing said resistanee-w nmd core and insulated therefrom and having said contact protruding to the exterior of said sheath.

7. An electrical heating unit comprising a core having a slot formed therein at a predetermined point, resistance material wound spirally on said core, an electrical contact in the form of a strip of metal bent intermediate its ends to offset portions thereof and inserted through said slot so that said offset portions bear against opposite faces of said core with a portion of said resistance clamped between said strip and core and a metal sheath enclosing said resistancen'onnd core and insulated therefrom and having said contact protruding to the exterior of said sheath.

S. An electrical heating unit COH'LPI'lSDf a core formed of a long narrow rectangu ar strip of asbestos interposed between strips of mica, said strip of asbestos being compara lively thick and said strips of mica being comparatively thin. Said core having a slot formed in each end thereof, electrical resistance wound spirally on said core from one end to the other, electrical contacts in the form of strips of metal bent intermediate their ends to form offset portions and inserted through said slots so as to have said offset portions bear against opposite faces of said core with the ends of said resistance clamped between said respective strips and the face of the core, a metal sheath enclosing, said resist ance-wound core and insulated therefrom and bent at right angles longitudinally so as to provide said unit with angularly disposed heating sections with said contacts protruding to the exterior of said sheath in the plane of one of said heating sections.

9. An electrical heating unit comprising a long narrow rectangular core of semi-rigid and semi-flexible material, electrical resistance spirally wound on said core, electrical contact members attached to said core and connected to said resistance and a metal sheath folded around said resistance-wound core and insulated therefrom and having said contact members extending to the exterior thereof, said unit havin a righbanglc bend formed therein longitudinally thereof so as to provide said unit with angularlr disposed heating sections.

10. An electrical heating unit comprisin a long narrow rectangular core of semi-rigi and semi-flexible material, electrical res1stance spirally wound on said core, electrical contactmembers attached to said core and connected to said resistance, and a metal sheath folded around said resistance-wound core and insulated therefrom and having said contact members extending to the exterior thereof, said unit having a right-angle hend formed therein lon itnclinnll thereof nearer one edge thereof t inn the other so as to provide said unit with singularly dis osed heating sections of relatively (lifierent Widths.

11. An electrical heating unit compris ing a core having a slot formed therein at a predetermined point, resistance material woundspirally on said core, an electrical contact in the form of n strip of metal inscrted through said slot and hzwing p0rtions thereof abutting against 0 )OSltB faces of said core with {L portion of sari resistance clumped between the strip and core, and means for clamping said contact strip sccnrely in place an said core.

Signed zit Rockford this 14th day of Febrnnry 1922i SEBRING I. PHELPS. 

